Pharmacokinetics for once-daily modified release formulation of tacrolimus hydrate in unrelated hematopoietic stem cell transplantation

A once-daily modified release formulation of oral tacrolimus (Tac QD) has been developed in response to the problem of nonadherence. However, there have been no data available about the efficacy of Tac QD conversion from intravenous Tac (Tac i.v.) in allogeneic hematopoietic stem cell transplantation (allo-SCT). We analyzed the pharmacokinetics (PK) of Tac QD in allo-SCT recipients. A total of 10 patients with hematological malignancies who received allo-SCT from unrelated donors were enrolled. Patients received Tac i.v. at 0.03 mg/kg a day before transplantation. Administration of Tac i.v. was converted to Tac QD at a 1:4 ratio when the patients had recovered from regimen-related gastrointestinal toxicity and could tolerate oral medication. After conversion, six out of 10 patients (60 %) showed a sustained decrease in Tac exposure and required dose adjustment. The conversion from Tac i.v. to Tac QD should be performed under close medical supervision. Area under the curve (AUC) and the trough of Tac QD showed a correlation, and the trough should be maintained above 7.5 ng/ml to provide an adequate AUC. Although four patients received bone marrow from an HLA DRB1 1 antigen-mismatched unrelated donor, no patients developed grade III-IV acute graft-versus-host disease (GVHD). The modification of Tac QD to maintain a whole-blood trough concentration above 7.5 ng/ml may be as effective as Tac BID.